This invention relates to apparatus and method for processing tobacco, and more particularly to applying a liquid additive foam to tobacco filler in the course of cigarette manufacturing.
During cigarette manufacturing, various materials may be added to tobacco filler to vary certain characteristics of the finished cigarette. The material most frequently added to the tobacco filler is flavoring. It is important that the material added to the tobacco filler be uniformly distributed throughout a given batch of filler so that all of the cigarettes produced from that batch are virtually identical. It is also important that the material be added uniformly so that an individual cigarette has consistent smoking characteristics from the first puff until the last puff.
Prior attempts to achieve uniform distribution of material added to tobacco filler have involved treating the tobacco filler early in the manufacturing process prior to delivering the filler to the cigarette making machine. However, when material is added early in the manufacturing process, some of the material may be lost during further processing, especially if the material added is volatile. In addition, some of the material may rub off in the cigarette making machine and foul up the cigarette making machine, causing it to be shut down periodically for cleaning. Shutting down the cigarette making machine for cleaning is expensive both because of the labor cost required for cleaning the machine and because of lost production time. Because many of the flavors added to cigarettes are expensive, loss of flavoring material, either because of its volatility or through build-up in the machine, can also be expensive.
It is desirable, therefore, to add the material to the tobacco filler late in the manufacturing process, preferably at the cigarette making machine itself, and in a uniform manner. Known methods of adding material at the maker have failed to achieve uniform distribution of the applied materials. For example, if material is added at the short tongue of the cigarette maker as in Nichols U.S. Pat. No. 4,409,995, the added material may be distributed in a uniform manner per unit length along the length of cigarette rod, but some of it may be concentrated on one side of the cigarette rod rather than being distributed throughout the cross section of the rod. If the material added is liquid, adding it in this manner may also result in streaking of the cigarette wrapper.
Further, it often is necessary to add only a minute quantity of material to the tobacco filler. In the past when this has been done, either at the cigarette making machine or earlier in the cigarette manufacturing process, the material has been applied as a dilute solution added to the tobacco filler. If such a solution is added at the cigarette making machine, as discussed, for example, in British patent application No. 2 128 873, which discloses the addition of a bonding agent in liquid form to smoking material, the excess liquid will often result in streaking of the cigarette wrapper, as discussed above. If the solution is added early in the manufacturing process, excess solution must be removed from the filler by drying, which results in additional expense.
In above-identified grandparent application Ser. No. 637,259, filed Aug. 3, 1984, now U.S. Pat. No. 4,619,276, it was disclosed that an additive material could be applied to the tobacco stream in a cigarette making machine as a liquid additive foam, either in the chimney - particularly in the belt guide section of the chimney, as the tobacco is deposited on the moving garniture tape, between the ecreteur and the short tongue, or at the short tongue. It was also disclosed that the liquid additive foam could be injected into the tobacco rod of a finished cigarette by injecting it through +h=end of the tobacco rod using a needle.
Because the additive material is applied as a foam, according to said copending application, a small amount could be more uniformly applied over a large amount of tobacco. Further, much less liquid or solvent need be used as compared to earlier methods of applying additive material.
However, even the small amount of liquid used in the liquid additive foam may mar the wrapper of a finished cigarette made with the treated tobacco filler. Further, where the liquid additive foam is a binder, intended to increase the firmness of the finished cigarette, if the filler is compressed to make the cigarette before the foam has set, the full firmness-increasing effect of the binder may not be realized.
It would be desirable to be able to dry and set a liquid additive foam that has been added to tobacco filler in a cigarette making machine, said drying and setting occurring prior to the incorporation of the filler into a finished cigarette.